option 82. Change a MAC-address.

Lars Jacobsen lars-jacobsen at newmail.dk
Wed Feb 27 13:12:13 UTC 2008

> Feb 27 11:37:13 helper dhcpd: DHCPDISCOVER from 00:dd:dd:dd:dd:a1 via 
> network optic: no free leases
> What I can do for quick release IP again? (Without checking a leases-file 
> maybe?)
> I've decreased a max-lease-time to 30sec. All work, but i've got a many 
> requests. It's not good.
> How I can set max-lease-time to 1day and quick release IP for request from 
> other MAC-address?
> Thanks.
> nick

Hi Nick

Nice job on class matching and logging in your config.
You are on the right track.
But as long a lease is running the server has no way reclaim it and assign 
it to another client - no matter if the client holding the lease is not 
active. Your pool is only one IP thus the  no free lease message. Only thing 
to do is wait until the lease expire and then the server will reclaim the 
lease and lease it to the new client (different MAC address). Or delete it 
from the lease database.
If you lower the lease time then it wil happen quicker, but the price is 
increased dhpc traffic (req/ack) as you have noticed.

There has been some discussions on making the DHCPd able to assign leases 
based on op. 82 circuit id /remote id (instead of client identifier/MAC 
address), but so far this has not been supported. But there has been some 
unofficial hacks doing it. Try search the list on opt. 82 if you feel 
comfortable fiddling with the code ;-)



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